Method of operating electric motors.



No. 740,101. PATENTED SEPT. 29, 1903.

W. A. DICK.

METHOD OF OPERATING ELECTRIC MOTORS.

APJE'LIOATION FILED. DBO. 29, 1902.

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No.740,101 I PATENTED SEPT. 29, 1903.-

W. A, DICK.

METHOD OF OPERATING ELECTRIC MOTORS.

APPLICATION FILED DEC. 29, 1902.

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ivo. 740,101.

UNITED SjIAfIjES Patented September 29, 1903.

'EENT QFFIQE-T WILLIAM A. DICK, OF WILKINSBIIRG, PENNSYLVANIA, ASSIGNORTO IVES'T INGI-IOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OFPENNSYLVANIA.

METHOD OF OPERATING ELECTRIC MOTORS.

SPECIFICATION formingpart of Letters Patent No. 740,101, dated.September 29, 1903;

Application filed December 29,1902. Serial Nor 137.072; (No model.) 7

1'0 all whom it may concern:

Be it known that I, WILLIAM A. DICK, a citi- Zen of the United States,residing at lVilkinsburg, in the county of Allegheny and State ofPennsylvania, have invented a new and useful Improvement in Methods ofOperating Electric Motors, of which the following is a specification.

My invention relates to the operation of electric motors at variablespeeds, and it has for its object to provide a method which maysuecessfull y and economically utilize the energy of a plurality ofcircuits of diiferent voltages, so as to provide a wide range of motorspeeds.

In practicing my invention I propose to utilize either a three -wirecircuit carrying either two or three different voltages ora plu ralityof separate circuits having different voltages in such manner as to makeeffective use of the different voltages more advantageously thanprevious practice has permitted.

In the accompanying drawings I have illusti'ated diagrammaticallycertain principal steps in my method.

Figure 1 shows a three-wire circuit in which a motor is connected foroperatiou at minimum speed. Fig. 2 is a similar view with the motorconnected to operateat a higher speed. Fig. 3 is a similar view showinga motor connected for a second higher speed, and Fig. 4 is a similarview showing a Fig. 5 is a diagram of a three-wire circuit havingdifferent voltagesbetween the respective main conductors and theintermediate conductor and showing a motor-armature connected to receivethe minimum voltage. Figs. 6 and 7 are views similar to Fig. 5, butrespectively showing the motor-armature connected to receive theintermediate and the maximum voltage. Figs. 8, 9, and 10 are viewssimilar to Figs. 5, 6, and 7, but showing two separate two-wire circuitsin lieu of a three-Wire circuit.

Referring first to Figs. 1 to 4 of the drawings, the main conductors 1and 2 and the intermediate or neutral conductor 3 may be supplied from asingle generator A, properly designed and constructed, as set forth, forexample, in patent to Michael von Dolivo -Dobrowols'ky, No. 513,006,dated January 16,

1804, or'these conductors may be supplied from two generators, inaccordance with the well-known Edison three-wire system, the singlegenerator being preferred, however, as involving less expense andcomplication.

The motor, or each of the motors if several are operated from thecircuit supplied by the generator 4:, comprises an armature 5 and afield-magnet 6, the winding of which is divided into two equal parts 7and 8, it being understood that the coils comprising one half of thewinding will be applied to pole-pieces which alternate with thosecarrying the coils constituting the other half of the winding in orderthat the magnetic circuits may be properly balanced. The winding 7 isconnected across the circuit 1 3 by means of a variable rheostat 9 andthe winding 8 is connected across the circuit 2 3 by means of a variablerheostat 10.

In Fig. 1 I have shown the apparatus arranged so that none of theresistance of either rheostat is included in circuit, and-consequentlythe motor has a field of maximum strength, and its armature beingconnected across the circuit which provides a minimum voltage the motorwill operate at a minimum speed. In order to gradually increase thespeed of the motor, either or both of the switch-arms 9 and 10 of therheostats 9 and 10 will be moved over the corresponding stationarycontacts to gradually include the resistance in the correspondingfield-magnet circuit.

As above suggested, the resistance of the rheostats 9 and 10 may be cutinto circuit either simultaneously or independently, and, in fact,either of the field-magnet circuits may be opened and the motor willstill continue to be operative.

In Fig. 2 the connections are thesame as those shown in Fig. 1 exceptthat the resistance of each of the rheostats 9 and 10 is in circuit withthe corresponding field-magnet winding, and consequently the motor has aminimum field strength for this connection of windings and the speed iscorrespondingly greater than with the arrangement shown in Fi 1.

In Fig.3 the armature 5 is connected across the circuit 1 2, andconsequently has impressed upon it double the voltage of the circuit 13, across which it was previously connected. The field-magnet windings 7and 8 are connected in series across the same circuit 1 2 withoutexternal resistance, and consequently the field is of maximum strengthfor this connection, and the motor will run at a speed corresponding tothe higher voltage applied to the armature. The speed of the motor maybe now gradually increased by moving the rheostatarms 9 and 10 eithersimultaneously or successit'ely to gradually weaken the field of themotor until the resistance is all in circuit, when the speed will bemaximum. This condition is illustrated in Fig. 4. Y

Referring now to Figs. 5 to 7 of the drawings, the three wire circuit 12 3 may be supplied from a single generator properly equipped orassociated with a suitable balancing means or by two generatorsconnected and operated in accordance with the wellknown Edisonthree-wire system of distribution, as has been already set forth inconnection with what is shown in the preceding figures of the drawings.In this case, however, the circuits 1 3 and 2 3 are supplied withdifferent voltages, which are designated on the drawings as voltage aand voltage A, the former being materially less than the latter. As hereindicated, the two voltages'are such that substantially one fourth ofthe field-magnet winding is connected across the circuit 1 2 and theremainder of the winding is connected across the circuit 2 3. If afour-pole motor be employed, the portion of the winding connected acrosscircuit 1 2 will be one coil (here designated as 7) and the portionconnected across circuit 2 3 will be three coils, (here designated as8.) Different voltages and a diiferent apportion ment of the windingwith reference to the circuits may of course be employed.

As represented in Fig. 5, the armature 5 is connected across the circuit1 3 of minimum voltage, and substantiaily one-half of each of theresistances 9 and 10 is connected in the corresponding field-magnetcircuit, it

being intended, however, as in the case al-- ready described, to startthe motor with noexternal resistance in circuit and to graduallyintroduce the resistance in order to increase the motor speed to thepoint where the armature is to be connected across the circuit of thenext higher voltage, this circuit in the present case being the circuit2 3 and this connection of the armature being indicated in Fig. 6. Inthis figure the resistances 9 and 10 are also illustrated as partiallyincluded in the field-magnet circuits by means of'the movable contactmembers 9 and 10. As in the preceding cases, this indicates anintermediate speed for this Voltage.

In Fig. 7 the armature is shown as conneeted between the conductors 1and 2, and

therefore as having impressed upon it the maximum voltage, which is thesum of the voltagesof the circuits 1 3 and 2 3. The field-magnet coilsare here also shown as all connected in series, the resistances 9 and 10being shown as partially included, and therefore as representing anintermediate speed for this connection of the armature and fieldmagnetwindings. Theinclusion of all of the resistances 9 and 10 in thefield-magnet circuit obviously corresponds to maximum speed.

Instead of employing three-wire circuits for securing either two orthree voltages I may employ separate circuits supplied from independentgenerators of different voltage. This I have illustrated in Figs. 8, 9,and 10, the circuit 1 3 being supplied with the lower voltage a and thecircuit 2 3 with the higher voltage A. As indicated in Fig. 8, thearmature is connected across the circuit 1 3 and a portion of thefield-magnet winding (here indicated as substantially one-fourth,)is-also connected-across this circuit, this portion of the winding beingdesignated as 7. The remainder of the field-magnet winding (designatedas 8) is connected across the circuit 2 3, each of the field-magnetcircuits being provided with external resistances, (designated,respectively,-as 9 and 10,) the active length of which is varied bymeans of movable members 9 and 10 in' the manner already described;

In Fig; 9 are represented the circuit connections for a higher speed,inwhich the armature 5 is connected across the higher voltagecireuit 2 3,the connection of the field-magnet circuits being the same as in Fig. 8.

In Fig. 10' the armature is connected the same as in Fig. 9 across thecircuit 2' 3, but the field-magnet winding is connected all in seriesacross the same circuit 2 3.

It will be understood that the resistances 9 and 10 will be adjusted tovary the motor field-magnet strength in accordance with the differentspeeds desired'in the manner already described in detail in connectionwith what is illustrated in Figs. 1 to 4.

WVhile I have illustrated shunt-windings only for the field-magnet ofthe motor, it will be understood that my invention is not limited' tothe operation of shunt-wound motors, since similar results may besecured by proper connection and adjustment of the circuits of compoundwindings. It will be also understood that the invention is not limitedto specific voltages and arrangements of circuits or to specificdivisions of the armaturewindings with reference to the circuits ofdifferentvoltage,provided an arrangement be adopted and employed whichwill be satisfactorily operative and be such-as to embody the essentialsteps constituting the method which will be hereinafter specificallypointed out in the claims.

I claim as my invention- 1. The method of operating an electric motor atVariable speeds from circuits having different voltages, which consistsin supplying a relatively low voltage to the armature and to a portionof the field-magnet winding for minimum speed, then progressivelyintroducing resistance into the field-circuit, then cutting out theresistance and supplying a higher voltage to the armature and to all thefield-magnet coils in series and finally progressively introducingresistance into the field-circuit.

2. The method of operating an electric motor at variable speeds fromcircuits having difi'erent voltages, which consists in supplying thelowest voltage to the armature an'd to a portion of the field-magnetcoils, then progressively introducing resistance into eachfield-circuit, then simultaneously cutting out the resistance andsupplying the armature an d entire field-Windin g with a higher voltageand finally progressively introducing resistance into the field-circuit.

3. The method of operating an electric motor at variable speeds fromcircuits having different voltages, which consists in connecting thearmature and a portion of the fieldmagnet winding across a low-voltagecircuit and another portion of the field-magnet winding across anotherlow-voltage circuit and varying the resistance of one or both of thefield-magnet circuits for one range of speed and connecting the armatureand the entire field-magnet winding across a high-voltage circuit andvarying the resistance of the fieldmagnet circuit for another range ofspeed.

4:. The method of operatingan electric motor at variable speeds,which'consists in connecting the armature and a portion of thefield-magnet winding across a low-voltage circuit and increasing theresistance of the field-magnet circuit for one range of speed and thenconnecting the armature and the entire field-magnet winding across ahighvoltage circuit and increasing the resistance of the field-magnetcircuit for another range of speed.

5. The method of operating an electric motor at variable speeds, whichconsists in connecting the armature and a portion of the field-magnetwinding across a low-voltage circuit and increasing the resistance ofthe field-magnet circuit for one range of speed, connecting the armatureand a greater length of the field-magnet winding across a highervoltagecircuit and increasing the resistance of the field-magnet circuit for ahigher range of speed and connecting the armature and the entirefield-magnet winding across a stillhigher-voltage circuit and increasingthe re sistance of the field-magnet circuit for a still higher range ofspeed.

6. The method of operating an electric motor at variable speeds whichconsists in supplying a relatively low voltage to the armature and to aportion of the field-magnet ing the resistance.

7. The method of operating an electric motor at variable speeds fromcircuits having different voltages which consists in supplying thearmature and a portion of the fieldqnagnet winding with energy from thecircuit having the lowest voltage and without external resistance forminimumspeed, supplying the armature and the entire shuntwinding, havingmaximum external resistance in its circuit, With energy from the circuithaving the highest voltage for maximum speed and varying resistance ofthe fieldmagnet circuit or circuits either with or without change ofarmature-voltage for intermediate speeds.

8. The method of operating an electric motor at variable speeds fromcircuits having diii'erent voltages which consists in transferring thearmature from one circuit to another and at the same time apportioningthe field-magnetwindin g to the respective circuits in accordance withthe voltages of said circuits and effecting intermediate changes inspeedby varying the amount of resistance in the field-magnet circuit orcircuits.

In testimony whereof I have hereunto subscribed my name this 17th day ofDecember,

WILLIAM A. DI 3K.

